Throughout their long career (which ended with Jerry Garcia’s death three years ago), the Grateful Dead were never so esteemed for their songwriting as for their live-concert chops and their status as a countercultural cult-magnet unlike any other. Thus theirs, among rock songbooks, doesn’t come to mind as natural fodder for a conventional stage book musical. The resulting curiosity “Cumberland Blues” does not, indeed, work very well — though mostly for reasons other than the music.

However, as stolidly conceived and juicelessly executed as the show largely is, it taps into a potential aud — the bewilderingly multigenerational, loyal “Deadheads” — that will likely be thrilled to hear favorite tunes in this new context. Unallied mainstream musical theater patrons will probably react much as Dead non-fans did to their music: i.e. with bored incomprehension. If the producers can find a way to tap that core following nationwide, they might have a review-resistant, whistle-stop-touring success on their hands. But rumored Broadway hopes should be red-lined ASAP.

The score is taken entirely (with the exception of “I Will Love You,” an innocuous new Robert Hunter-Greg Anton ballad) from two albums often considered this S.F.-based band’s finest studio efforts: “Workingman’s Dead” and “American Beauty” (both released in 1970). Those songs — including such staples as “Uncle John’s Band,” “Friend of the Devil,” “Ripple” and “Box of Rain” — are surprisingly well integrated into the narrative, despite unaltered original lyrics.

As played by an onstage quintet, with cast vocalizing, they’re pleasant but quite samey; amplified-acoustic accompaniment eschews the Dead’s psychedelic flavors for a bland constancy of pop-lite bluegrass.

The bigger problem, though, lies in Michael Norman Mann’s script, which provides a thin, rote clothesline on which to hang 18 songs. It’s ye olde prodigal son saga, set in period-vague Maryland mining town Cumberland. Crusty, widowed coalmine patriarch Pete Jones (Stephen Gill) is dying of “black lung”; he sends out a call to “get my boys back home” so they can all “make peace” before his death.

The three errant sons in question are honest if dim Ron (Colin Thomson), ne’er-do-well hustler Mick (Jonathan Williams) and long-absent eldest Pete Jr. (Ric Iverson), who’s become a brimstone-style travelin’ preacher. Each pines for Dad’s adopted daughter and business helper Mindy (Marcia Pizzo). But only Junior still has a hold on her heart.

Subplots are scant, sole notable one being Mick’s chasing by the girl he once “ruined” and abandoned (a painfully hammy Lisa Recker). But the main threads aren’t any better developed. There’s no character depth here, no current of genuine feeling, just lame humor and a series of earnest cliches (e.g. “If it’s the right thing to do, why’s it so tough?”) strung together as song cues. Mann seems happy to blow all potential dramatic highlights — Pop dies offstage (a local doctor announces “Sorry, he’s gone,” and that’s it), while book’s ending seems to be MIA.

Director Randall King, stuck with a set design that minimizes useable playspace, provides little zest or resourcefulness. A choreographer (Tyler Risk) is credited — but surely the dull-to-nil movement here could have been improvised. Playing underwritten archetypes, the actors add little charisma. They’re also a mediocre vocal ensemble — Williams’ quavery tenor comes closest to making any distinctive impression.

On the other hand, an opening-night crowd of Dead loyalists applauded every number and howled at every timid joke. “Cumberland Blues” may not need to be good musical theater — it just needs to travel fleetly (and inexpensively) enough to milk residual Deadhead pockets around the country.

Cumberland Blues

(MUSICAL; STAGE DOOR THEATER; 555 SEATS; $ 38 TOP)

Production

SAN FRANCISCO A Cumberland Blues Co. presentation, in association with San Jose Stage Co., of a musical in two acts with songs by Jerry Garcia and Robert Hunter, book by Michael Norman Mann, additional music by Phil Lesh and Greg Anton. Directed by Randall King. Musical director/arranger, Don Dally; choreographer, Tyler Risk.